Issue 51

M.G. Masciotta et alii, Frattura ed Integrità Strutturale, 51 (2020) 423-441; DOI: 10.3221/IGF-ESIS.51.31 439 Figure 17: Maximum eigenvalue of the fracture strain tensor E f at scenario DS5. Figure 18: Minimum eigenvalue of the stress tensor T [Pa] at scenario DS5. C ONCLUSIONS ettlements represent one of the main causes of collapse in arched structures and not all the aspects related to this phenomenon have been completely explored in the literature, as for instance their effects on arches dynamic properties. The correct dynamic characterization of this kind of structures undergoing supports settlements is fundamental to timely detect the occurrence of serious damage mechanisms and prevent unexpected failures. This paper focused on the dynamic characterization of a segmental masonry arch with one settled support, from both the experimental and the numerical point of view. The arch specimen, tested in the Structural Laboratory of University of Minho, was progressively damaged by applying uniform increasing displacements at one abutment. After each displacement stage, dynamic identification tests were performed to estimate, via the Enhanced Frequency Domain Decomposition and the Stochastic Subspace Identification methods, the modal characteristics of the system in terms of frequencies, mode shapes and damping ratios. Despite the low displacement rate applied to the support, significant changes affected the eigenfrequencies and damping ratios of the arch; in particular, decreases of about 36% and 22% were recorded for the first and fourth eigenfrequencies as a consequence of a total settlement of 3 mm. This fact is likely connected to the deformations associated to the first and fourth mode shapes of the arch (anti-symmetric eigenmodes) due to the abutment settlement. Analyzing the evolution of the modal features allows quantifying the effects that the spreading supports can have on the dynamic behavior of segmental masonry arches, both at global and local levels, and demonstrating the high vulnerability of such structures even to incipient support settlements. From the numerical point of view, with the purpose of reproducing the dynamic behavior identified along the test stages, a numerical method relying on the coupled application of linear perturbation and modal analysis, implemented in the non- S